Re: [PATCH] eal/linux: verify mmu type for DPDK support (ppc64le)

[Thomas Monjalon <thomas@monjalon.net>]

11/10/2023 00:51, David Christensen:
> IBM POWER systems support more than one type of memory management unit
> (MMU).  The Power ISA 3.0 specification, which applies to P9 and later
> CPUs, defined a new Radix MMU which, among other things, allows an
> anonymous memory page mapping to be converted into a hugepage mapping
> at a specific address. This is a required feature in DPDK so we need
> to test the MMU type when POWER systems are used and provide a more
> useful error message for the user when running on an unsupported
> system.
> 
> Bugzilla ID: 1221
> Suggested-by: Thomas Monjalon <thomas@monjalon.net>
> Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
> ---
> --- a/lib/eal/linux/eal.c
> +++ b/lib/eal/linux/eal.c
> +/*
> + * IBM POWER systems support more than one type of memory management unit (MMU).
> + * The Power ISA 3.0 specification, which applies to P9 and later CPUs, defined
> + * a new Radix MMU which, among other things, allows an anonymous memory page
> + * mapping to be converted into a hugepage mapping at a specific address. This
> + * is a required feature in DPDK so we need to test the MMU type when POWER
> + * systems are used.
> + */
> +static bool
> +is_mmu_supported(void)
> +{
> +#ifdef RTE_ARCH_PPC_64
> +	static const char proc_cpuinfo[] = "/proc/cpuinfo";
> +	static const char str_mmu[] = "MMU";
> +	static const char str_radix[] = "Radix";
> +	char buf[512];
> +	char *ret = NULL;
> +	FILE *f = fopen(proc_cpuinfo, "r");
> +
> +	if (f == NULL) {
> +		RTE_LOG(ERR, EAL, "Cannot open %s\n", proc_cpuinfo);
> +		return false;
> +	}
> +
> +	/*
> +	 * Example "MMU" in /proc/cpuinfo:
> +	 * ...
> +	 * model	: 8335-GTW
> +	 * machine	: PowerNV 8335-GTW
> +	 * firmware	: OPAL
> +	 * MMU		: Radix
> +	 * ... or ...
> +	 * model        : IBM,9009-22A
> +	 * machine      : CHRP IBM,9009-22A
> +	 * MMU          : Hash
> +	 */
> +	while (fgets(buf, sizeof(buf), f) != NULL) {
> +		ret = strstr(buf, str_mmu);
> +		if (ret == NULL)
> +			continue;
> +		ret += sizeof(str_mmu) - 1;
> +		ret = strchr(ret, ':');
> +		if (ret == NULL)
> +			continue;
> +		ret = strstr(ret, str_radix);
> +		break;
> +	}
> +	fclose(f);
> +	if (ret == NULL)
> +		rte_eal_init_alert("DPDK on PPC64 requires radix-mmu.");
> +	return (ret != NULL);
> +#else
> +	return true;
> +#endif
> +}

I feel this function should not be implemented in the common EAL.
What about adding a new function in lib/eal/ppc/ ?
And add the "return true" for other architectures?